Expandable intervertebral spacer

ABSTRACT

A spacer for separating bones of a joint, the spacer includes a first endplate configured to engage a first bone of the joint; a second endplate configured to engage a second bone of the joint; and an actuation subassembly comprising a drive nut, a drive screw coupled to the drive nut, and a cam frame coupled to the drive screw, wherein the cam frame is disposed between the first endplate and the second endplate, wherein the cam frame comprises a proximal frame end, a distal frame end, and lateral frame sides, wherein cams disposed on the lateral frame sides selectively engage at least one of the first endplate or the second endplate.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/970,598, filed Dec. 16, 2015, which is incorporated by referenceherein in its entirety for all purposes.

FIELD OF THE INVENTION

This invention relates to stabilizing adjacent vertebrae of the spine byinserting an intervertebral spacer, and more particularly anintervertebral spacer that is adjustable in height.

BACKGROUND

The vertebral or spinal column (spine, backbone) is a flexible assemblyof vertebrae stacked on top of each other extending from the skull tothe pelvic bone which acts to support the axial skeleton and to protectthe spinal cord and nerves. The vertebrae are anatomically organizedinto four generalized body regions identified as cervical, thoracic,lumbar, and sacral; the cervical region including the top of the spinebeginning in the skull, the thoracic region spanning the torso, thelumbar region spanning the lower back, and the sacral region includingthe base of the spine ending with connection to the pelvic bone. Withthe exception of the first two cervical vertebrae, cushion-like discsseparate adjacent vertebrae, i.e. intervertebral discs.

The stability of the vertebral column during compression and movement ismaintained by the intervertebral discs. Each disc includes a gel-likecenter surrounded by a fibrous ring. The gel-like center, i.e. nucleuspulposus, provides strength such that the disc can absorb and distributeexternal loads and contains a mixture of type II-collagen dispersed in aproteoglycan matrix. The fibrous ring, or annulus fibrosus, providesstability during motion and contains laminated rings of type-I collagen.Thus, the annulus fibrosis and the nucleus pulposus are interdependent,as the annulus fibrosis contains the nucleus pulposus in place and thenucleus pulposus aligns the annulus fibrosus to accept and distributeexternal loads. The integrity of the composition and structure of theintervertebral disc is necessary to maintain normal functioning of theintervertebral disc.

Many factors can adversely alter the composition and structure of theintervertebral disc, such as normal physiological aging, mechanicalinjury/trauma, and/or disease, resulting in impairment or loss of discfunction. For example, the content of proteoglycan n the nucleuspulposus declines with age, thus, it follows that the ability of thenucleus pulposus to absorb water concurrently declines. Therefore, innormal aging the disc progressively dehydrates, resulting in a decreasein disc height and possible de-lamination of the annulus fibrosus.Mechanical injury can tear the annulus fibrosis allowing the gel-likematerial of the nucleus pulposus to extrude into the spinal canal andcompress neural elements. Growth of a spinal tumor can impinge upon thevertebrae and/or disc potentially compressing nerves.

Bones of the spine, and bony structures, generally, are susceptible to avariety of weaknesses that can affect their ability to provide supportand structure. Weaknesses in bony structures have numerous potentialcauses, including degenerative diseases, tumors, fractures, anddislocations. Advances in medicine and engineering have provided doctorswith a plurality of devices and techniques for alleviating or curingthese weaknesses.

In some cases, the spinal column, in particular, requires additionalsupport in order to address such weaknesses. One technique for providingsupport is to insert a spacer between adjacent vertebrae.

SUMMARY

In accordance with an embodiment of the disclosure, a spacer forseparating bone of a joint may be provided, wherein the spacer maycomprise: a first endplate configured to engage a first bone of thejoint; a second endplate configured to engage a second bone of thejoint; and an actuation subassembly comprising a drive nut, a drivescrew coupled to the drive nut, and a cam frame coupled to the drivescrew, wherein the cam frame is disposed between the first endplate andthe second endplate, wherein the cam frame comprises a proximal frameend, a distal frame end, and lateral frame sides, wherein cams disposedon the lateral frame sides selectively engage at least one of the firstendplate or the second endplate.

In accordance with an embodiment of the disclosure, a method ofseparating bones of a joint may be provided, wherein the method maycomprise inserting a spacer between bones of the joint; and translatinga cam frame along a longitudinal axis of the spacer, wherein camsdisposed on the cam frame engage at least one of a first endplate and/ora second endplate increasing a height of the spacer.

BRIEF DESCRIPTION OF THE DRAWINGS

These drawings illustrate certain aspects of some examples of thepresent invention, and should not be used to limit or define theinvention.

FIG. 1 is a perspective view of a spacer in a collapsed position inaccordance with example embodiments;

FIG. 2 is a perspective view of a spacer in an expanded position inaccordance with example embodiments;

FIG. 3 is an exploded view of a spacer in accordance with exampleembodiments;

FIGS. 4 and 5 illustrate an endplate of a spacer in accordance exampleembodiments;

FIG. 6 illustrates a cam frame of a spacer of in accordance with exampleembodiments;

FIGS. 7 and 8 illustrate cam pins in accordance with exampleembodiments.

FIG. 9 illustrates a front plate in accordance with example embodiments.

FIGS. 10 and 11 illustrate an actuation subassembly positioned with anendplate in accordance with example embodiments;

FIGS. 12 and 13 illustrate a spacer insertion device in accordance withexample embodiments;

FIG. 14 is a perspective view of a spacer in a collapsed position inaccordance with example embodiments;

FIG. 15 is a perspective view of a spacer in an expanded position inaccordance with example embodiments;

FIG. 16 is an exploded view of a spacer in accordance with exampleembodiments;

FIG. 17 illustrates a front plate of a spacer in accordance with exampleembodiments;

FIG. 18 illustrates a spacer in accordance with example embodiments;

FIG. 19 is a perspective view of a spacer in a collapsed position inaccordance with example embodiments;

FIG. 20 is a perspective view of a spacer in an expanded position inaccordance with example embodiments;

FIG. 21 is an exploded view of a spacer in accordance with exampleembodiments;

FIG. 22 illustrates a spacer in accordance with example embodiments;

FIG. 23 is a perspective view of a spacer in a collapsed position inaccordance with example embodiments;

FIG. 24 is a perspective view of a spacer in an expanded position inaccordance with example embodiments;

FIG. 25 is an exploded view of a spacer in accordance with exampleembodiments;

FIG. 26 illustrates an endplate of a spacer in accordance exampleembodiments;

FIG. 27 illustrates a cam frame of a spacer in accordance with exampleembodiments;

FIG. 28 illustrates a cam of a spacer in accordance with exampleembodiments;

FIGS. 29 and 30 illustrate an actuation subassembly positioned with anendplate in accordance with example embodiments;

FIG. 31 is a perspective view of a spacer in a collapsed position inaccordance with example embodiments;

FIG. 32 is a perspective view of a spacer in an expanded position inaccordance with example embodiments;

FIG. 33 is an exploded view of a spacer in accordance with exampleembodiments;

and

FIG. 34 illustrates a spacer in accordance with example embodiments.

DETAILED DESCRIPTION

Embodiments are directed to a spacer that may be inserted between twoadjacent bony surfaces to facilitate separation of the bones, and ifdesired, to promote the fusion of bony surfaces. Although intended to beuseful with any adjacent bony surface in which fusion is desired, thespacer may advantageously be applied to insertion between two adjacentvertebral bodies in any section of the spine, including the cervical,thoracic, lumbar, and sacral vertebral sections. Additionally, thespacer may be implanted through an anterior, anterolateral, posterior,posterolateral, lateral, or any other suitable approach. More than onespacer may be implanted within the body, for example between successiveor separated vertebrae, between adjacent vertebrae. The use of multiplespacers is particularly advantageous for patients whose back pain is notlimited to a localized area, or for patients whose localized damage hasprogressed to other areas of the spine.

The spacer and methods for its insertion can be used in a treatmentprotocol for any of a wide variety of conditions in a patient involvingdiseased or damaged bony structures. The patient can be a human being.Additionally, it is contemplated that the spacer may be useful inveterinary science for any animal having adjacent bony structures to befused. The spacer can collapse, for example, to approximately one halfof an expanded size. When in this collapsed configuration, the spacercan be inserted into a space through a small incision and narrowpathways, using appropriate minimally-invasive techniques, and can bepositioned within the space between adjacent bones, and there expandedto a desired therapeutic height. The incision may be short, for exampleabout one inch in length, which is smaller than the spacer in anexpanded configuration. If the desired position and/or expansion are notachieved, the spacer can be collapsed, repositioned, and re-expanded insitu.

Although the spacer is exemplified herein for use in the spine, thespacer is contemplated for fusion of any bony structures. While thespacers are described herein using several varying embodiments, thespacers are not limited to these embodiments. An element of oneembodiment may be used in another embodiment, or an embodiment may notinclude all described elements.

With reference now to FIGS. 1-3, embodiments of spacer 100 may compriseendplates 102 and actuation subassembly 104. In the embodiment shown,endplates 102 may be generally symmetrical, and spacer 100 can beimplanted with either endplate 102 positioned superior with respect tothe other. In other embodiments, they may be dissimilar, and aparticular orientation may then be advantageous or necessary. Whilespacer 100 shown on FIGS. 1-3 may be implanted using a variety ofapproaches, spacer 100 may be particularly suitable for a lateralapproach.

Spacer 100 forms a distal end 106 which may be inserted first into thebody, and which can be tapered to facilitate insertion between bodytissues. Spacer 100 also forms a proximal end 108, to which a spacerinsertion device (e.g. 202 shown on FIGS. 12 and 13) may be connected.Spacer 100 may be inserted in a collapsed position, as shown on FIG. 1.Distal end 106 and proximal end 108 define a spacer longitudinal axis110. The spacer 100 may be expanded, as shown on FIG. 2, after it hasbeen inserted. To expand spacer 100, cam frame 112 (best seen on FIG. 3)may be displaced related to endplates 102. As the cam frame 112translates along spacer longitudinal axis 110, cam frame 112 engages campins 114, driving them outward and, in turn, pushing endplates 102relatively apart such that a height of spacer 100 may be increased. Aswill be discussed in more detail below, translation of cam frame 112 maybe effected by rotation of drive nut 113.

Turning now to FIGS. 4 and 5, embodiments of endplates 102 will now bedescribed. It should be understood that the endplates 102 may besymmetrical so the description may equally apply to either of endplates102. Endplates 102 may have a plate proximal end 116 and a plate distalend 118. Nose 120 at plate distal end 118 may be tapered or otherwiseformed to facilitate insertion into a desired location. As best seen onFIG. 4, endplates 102 may further comprise an outer facing surface 122connecting plate proximal end 116 and plate distal end 118. Asillustrated, endplates 102 may also comprise lateral sides 124.Endplates 102 may further comprise an inner facing surface 126. Innerfacing surface 126 may have a recessed portion 128 in which cam frame112 may be received. In the illustrated embodiment, endplates 102 mayfurther comprise a cutout 130 for receiving drive screw 132 (e.g., shownon FIG. 3).

In some embodiments, endplates 102 may further comprise through openings136. Through openings 136 may form an opening in endplates 102 thatextends from outer facing surface 122 to inner facing surface 126. Thethrough opening 136, in an exemplary embodiment, may be sized to receivebone graft or similar bone growth inducing material and further allowthe bone graft or similar bone growth inducing material to be packed ina central opening 138 in cam frame 112 (best seen on FIG. 6).

With specific reference to FIG. 4, the outer facing surfaces 122 ofendplates 102 may be flat and generally planar to allow the outer facingsurfaces 122 to engage with the adjacent tissue (e.g., vertebral body).Alternatively, not shown, the outer facing surfaces 122 may be curved,convexly or concavely to allow, for a greater or lesser degree ofengagement with the adjacent tissue. It is also contemplated that theouter facing surfaces 122 can be generally planar but include agenerally straight ramped surface or a curved ramped surface. Wherepresent, the ramped surface may allow for engagement with the adjacenttissue in a lordotic fashion. In the illustrated embodiment, the outerfacing surfaces 122 comprise texturing 140, for example, to aid ingripping the adjacent tissue. Although not limited to the following, thetexturing can include teeth, ridges, friction increasing elements,keels, or gripping or purchasing projections.

As seen in FIGS. 6a and 6b , the endplates 102 may further include aplurality of holes 142. In some embodiments, holes may be blind holesthat do not extend through outer facing surfaces 122. The holes 42 maybe configured to receive cam pins 114, for example. The holes 142 maydefine a cam contact surface in which motion of the cam pins 114 istransferred to endplates 102. As illustrated, the holes 142 may bearranged in a row in each lateral side 124 of the endplates 102. In theillustrated embodiment, there are three holes 142 in each lateral side124. However, it should be understood that the number and arrangement ofholes 142 in endplates 102 may be selected as desired for a particularapplication. In addition, guide pin holes 144 may be also be disposed inat least one of the endplates 102. Guide pins 146 (e.g., shown on FIG.3) may be disposed in fastener holes 144, for example, to guideexpansion of endplates 102.

Endplates 102 may additionally, or alternatively, be resilient, so thatthey may conform to bony surfaces, forming a more stable supportplatform. Accordingly, endplates 102 can be fabricated from a polymericmaterial, a naturally resilient material, or a resilient metal, forexample a shape memory alloy, or any other resilient biocompatiblematerial of sufficient strength and durability for separating boneswithin the body.

Turning now to FIGS. 3 and 6, cam frame 112 will now be described inmore detail with respect to particular embodiments. As illustrated, camframe 112 may comprise proximal frame end 148, distal frame end 150, andlateral frame sides 152. Lateral frame sides 152 may extend fromproximal frame end 148 to distal frame end 150. Proximal frame end 148,distal frame end 150, and lateral frame sides 152 may define centralopening 138 in cam frame 112. Opening 154 may be formed in proximalframe end 148 through which drive screw 132 may be disposed. Retainingslots 156 may be formed in proximal frame end 148 that intersect opening154. One or more screw retaining plates 158 may be inserted intoretaining slots 156 to retain drive screw 132.

In some embodiments, cam slots 160 may be formed in lateral frame sides152. As illustrated three cam slots 160 may be formed in each of lateralframe sides 152. However, it should be understood that more or less thanthree cam slots 160 may be used. The number of cam slots 160 generallymay correspond to the number of cam pins 114. At least a portion of campins 114 may be disposed in a corresponding one of cam slots 160. By wayof example, each of cam pins 114 may include a protuberance, such asridge 162 (best seen on FIGS. 7 and 8). The ridge 162 may ride in camslots 160. The cam slots 160 may include drive surfaces 164 that engagecam pins 114. The cam slots 160 may operate to change the direction ofthe linear movement of cam frame 112. For example, movement of the camframe 112 along the spacer longitudinal axis 110 may be changed tomovement of cam pins 114 in a direction generally transverse to spacerlongitudinal axis 110. As the cam frame 112 is moved, for example, alongthe spacer longitudinal axis 110, the cam slots 160 may engage the campins 114 to drive the cam pins 114 against the endplates 102, pushingendplates 102 relatively apart such that a height of spacer 100 may beincreased. Cam slots 160 may be arranged so that expansion may beachieved with advancement or withdrawal of cam frame 112 with movementof the cam frame 112 in the opposite direction causing the cam slots 160to engage the cam pins 114 to drive the cam pins 114 into a collapsedposition, thus collapsing the endplates 102. As illustrated, the camslots 160 may be angled with respect to spacer longitudinal axis 110. Aswill be appreciated, the angle of cam slots 160 may be adjusted tomodify expansion of endplates 102.

Turning now to FIG. 7, an example cam pin 114 is illustrated in moredetail in accordance with embodiments of the present disclosure. In theillustrated embodiment, cam pin 114 may comprise an elongated bodyportion 166 and ridge 162. In operation, the cam pin 114 may engage oneof endplates 102 driving it outward. As illustrated, ridge 162 mayproject from elongated body portion 166 and extend at an angle withrespect to the elongated body portion 166. As previously described,ridge 162 may ride in cam slots 160 of cam frame 112. Ridge 162 mayinclude a drive surface 170 and a return surface 172. Motion of camframe 112 may be transferred to cam pin 114 through drive surface 170 asendplates 102 are being driven outward, while motion of cam frame 112may be transferred to cam pins 114 through return surface 172 asendplates 102 are being retracted. FIG. 8 illustrates an alternativeembodiment of a cam pin 114 in which drive surface 170 is disposed on anopposite side of ridge 162 from the embodiment shown on FIG. 8. Thepositioning of drive surface 170 with respect to return surface 172 maydepend on the angle of the cam slot 160 into which the cam pin 114 maybe disposed. Depending on the angle of cam slots 160, the cam pins 114of FIGS. 7 and 8 may be used separately or in combination.

Front plate 174 of spacer 100 is shown in more detail on FIGS. 3 and 9in accordance with example embodiments. As best seen on FIG. 9, frontplate 174 may include a plate body 176 and an extension 178. Front plate174 may be arranged so that extension 178 extends from plate body 176toward spacer distal end 106. Plate body 176 may also include outerfacing surfaces 180. In the illustrated embodiment, the outer facingsurfaces 180 comprise texturing 182, for example, to aid in gripping theadjacent tissue. Although not limited to the following, the texturingcan include teeth, ridges, friction increasing elements, keels, orgripping or purchasing projections. In some embodiments, extension 178may also include extension guide pin holes 184 for receiving guide pins146. As best seen on FIG. 3, front plate 174 may be disposed plateproximal end 116 with extension 178 extending between endplates 102.Front plate 174 may be positioned so that guide pin holes 184 may alignwith guide pin holes 144 in endplates 102, Front plate 174 may furtherinclude a through bore 186, which may extend through front plate 174,for example, in a direction of spacer longitudinal axis 110. Plate body176 may further comprise an insertion tool engagement 134, best seen onFIG. 3, which engages a corresponding engagement of spacer insertiondevice (e.g., 202 on FIGS. 12 and 13).

FIGS. 10 and 11 illustrate actuation subassembly 104 in accordance withembodiments of the present invention. Embodiments of actuationsubassembly 104 will also described with additional reference to FIG. 3.Action subassembly 104 may extend between endplates 102. In theillustrated embodiments, one of the endplates 102 has been removed tobetter show actuation subassembly 104. FIG. 10 illustrates the actuationassembly 104 in a collapsed position, and FIG. 11 illustrates theactuation assembly 104 in an expanded position.

As illustrated, actuation subassembly 104 may comprise cam frame 112,drive screw 132, and drive nut 113. Cam frame 112 may be displacedrelative to endplates 102 by rotation of drive nut 113 which in turnmoves drive screw 132 and cam frame 112 along spacer longitudinal axis110. In some embodiments, rotation of drive nut 113 may cause cam frame112 to translate a path along spacer longitudinal axis 110. A spacerinsertion device (e.g., 202 on FIGS. 12 and 13) may interact with drivenut 113 to cause rotation of drive nut 113 so that cam frame 112 may beadvanced and/or withdrawn. As the cam frame 112 is advanced, the camframe 112 may drive the cam pins 114 causing them to push endplates 102from a collapsed position (e.g., shown on FIG. 10) to an expandedposition (e.g., shown on FIG. 11).

Embodiments of drive nut 113 may also include a nut through bore 188,which may be threaded as best seen on FIG. 3. Drive screw 132 mayinclude a threaded portion 190. Threaded portion 190 may threadinglyengage nut through bore 188 so that drive nut 113 may be retained ondrive screw 132. Embodiments may further include a first ring 192 and asecond ring 194, which one or both may be in the form of a c-ring orother suitable device. In some embodiments, first ring 192 may be awasher and second ring 194 may be a c-ring. In some embodiments, firstring 192 and/or second ring 194 may be compressible. In someembodiments, first ring 192 and/or second ring 194 may be retained oncorresponding grooves found on extension 196 from head portion 198 ofdrive nut 113. When assembled, first ring 192 may be disposed betweenendplates 102 and drive nut 113. In some embodiments, extension 196 ofdrive nut 113 may be secured in through bore 186 of front plate 174. Forexample, extension 196 may threadingly engage through bore 186. Secondring 194 may be disposed on extension 196 during insertion into throughbore 186 of endplates 102 and then expand, thus securing drive nut 113to front plate 174.

In some embodiments, drive screw 132 may be secured in drive nut 113 atone end and be secured to cam frame 112 at another end. Drive screw 132may include a retainer groove 200, best seen on FIG. 3. As illustrated,retainer groove 200 may be disposed at an opposite end of drive screw132 from threaded portion 190. Drive screw 132 may extend into opening154 in cam frame 112. One or more screw retaining plates 158 mayinserted into retaining slots 156 to engage drive screw 132. Forexample, screw retaining plates 158 may engage retainer groove 200 sothat drive screw 132 may be retained in opening 154.

FIGS. 12 and 13 illustrate spacer insertion device 202 in accordancewith embodiments of the present invention. Spacer insertion device 202may be used to engage spacer 100 during its insertion into a patient andalso to actuate spacer 100 after its insertion. As illustrated, spacerinsertion device 202 may comprise a handle portion 204 and an implantholder portion 206. Spacer insertion device 202 may further comprise aninner shaft 208 and an outer shaft 210. As best seen on FIG. 13, innershaft 208 may include a threaded end 212 onto which the spacer 100 maybe threaded. For example, threaded end 212 may thread into a threadedopening 214 of drive screw 132 (e.g., shown on FIG. 3). Implant holderportion 206 may also include ears 216 (or other projections) that engagecorresponding insertion tool engagements 134 (e.g., shown on FIG. 3) offront plate 174. Implant holder portion 206 may also include drive nutinterface 218 (best seen on FIG. 13) that engages drive nut 113 to causerotation of drive nut 113.

Referring now to FIGS. 14-18, in an alternative embodiment, in whichlike numbers correspond to like elements in other embodiments herein, aspacer 100 is illustrated. As illustrated, the spacer 100 may compriseendplates 102 and actuation subassembly 104. Actuation subassembly 104may comprise drive nut 113, drive screw 132, and cam frame 112. Spacer100 may further comprise front plate 174. As previously described, camframe 112 may engage cam pins 114 driving them into endplates 102,forcing the endplates 102 apart. Embodiments of spacer 100, and thevarious components thereof, shown on FIGS. 14-18 may be similar infunction and operation to spacer 100 shown on FIGS. 1-11 except thatplate body 176 of front plate 174 may further include bone fastenerreceiving holes 220. Bone fastener receiving holes 220 may extendthrough front plate 174 at an angle with respect to spacer longitudinalaxis 110. Bone fastener receiving holes 220 may be sized and configuredto receive a bone fastener 222, best seen on FIG. 18. Bone fastener 222may be any suitable fastener for securing front plate 174 to adjacenttissue, such as vertebral bodies. Examples of suitable bone fasteners222 may include, without limitation, bone screws and bone shanks. Asbest seen on FIG. 18, front plate 174 may further include a blockingscrew 224. Blocking screws 224 may be rotated to block bone fasteners222 and retain bone fasteners 222 in bone fastener receiving holes 220.While spacer 100 shown on FIGS. 14-18 may be implanted using a varietyof approaches, spacer 100 may be particularly suitable for a lateralapproach.

Referring now to FIGS. 19-22, in an alternative embodiment, in whichlike numbers correspond to like elements in other embodiments herein, aspacer 100 is illustrated. As illustrated, the spacer 100 may compriseendplates 102 and actuation subassembly 104. Actuation subassembly 104may comprise drive nut 113, drive screw 132, and cam frame 112. Spacer100 may further comprise front plate 174. Front plate 174 may comprisebone fastener receiving holes 220 for receiving bone fasteners 222.Blocking screw 224 may be disposed in front plate 174 and may be rotatedto retain bone fasteners 222 in bone fastener receiving holes 220. Aspreviously described, cam frame 112 may engage cam pins 114 driving theminto endplates 102, forcing the endplates 102 apart. While spacer 100shown on FIGS. 19-22 may be implanted using a variety of approaches,spacer 100 may be particularly suitable for an anterior or anterolateralapproach.

Embodiments of spacer 100, and its various components, shown on FIGS.19-22 may be similar in function and operation to embodiments of spacer100 shown on FIGS. 19-22, except that spacer 100 may have a differentconfiguration. By way of example, instead of one through opening 136 inendplates 102, each endplate 102 may comprise a pair of through openings136. In addition, endplates 102 may also comprise a central extension226 that extends from plate proximal end 116 to plate distal end 118.Additionally, cam frame 112 (best seen on FIG. 21) may be open at oneend, for example, the distal frame end 150, which may be oppositeopening 154. Moreover, a central frame extension 228 may extend fromproximal frame end 148 between lateral frame sides 152. With respect toendplates 102, one of the endplates 102 (e.g., the uppermost endplate)may comprise front sockets 230 for receiving bone fasteners 222. Blocksscrews 224 may be disposed in front sockets 230 for retaining bonefasteners 222 therein. Additionally, middle plate 232 may be disposedbehind front plate 134, as best seen on FIG. 21. Middle plate 232 mayreceive drive screw 132 and have wings 234 that fit in correspondinggrooves of endplates 102. While drive nut 113 has previously beendescribed as being a separate components, embodiments may include adrive nut 113 integral to, or otherwise formed with, drive screw 132, asbest seen on FIG. 21.

Referring now to FIGS. 23-30, in an alternative embodiment, in whichlike numbers correspond to like elements in other embodiments herein, aspacer 100 is illustrated. As illustrated, the spacer 100 may compriseendplates 102 and actuation subassembly 104. Actuation subassembly 104may comprise drive nut 113, drive screw 132, and cam frame 112. Spacer100 may further comprise front plate 174. Cam frame 112 may comprisecams 236 coupled thereto that engage endplates 102, force the endplates102 apart, as cam frame 112 is translated. While spacer 100 shown onFIGS. 23-30 may be implanted using a variety of approaches, spacer 100may be particularly suitable for a lateral approach. Embodiments ofspacer 100, and the various components thereof, shown on FIGS. 23-30 maybe similar in function and operation to spacer 100 shown on FIGS. 1-11except that cam frame 112 may comprise cams 236 instead of cam slots160.

With reference to FIGS. 25 and 27-30, embodiments of cam frame 112 willnow be described in more detail. As previously described, cam frame 112may comprise proximal frame end 148 and distal frame end 150, which areboth coupled by lateral frame sides 152. In some embodiments, camclearance slots 238 may be formed on lateral frame sides 152. Camclearance slots 238 may be sized and configured to allow forunobstructed rotation of cams 236, for example. Cams 236 may be coupledto cam frame 112. As illustrated, cams 236 may be coupled in camclearance slots 238. Cam pins 240 may pivotably retain cams 236 inconnection with cam frame 112. In the illustrated embodiment, cam pins240 may be unitary, but cam pins 240 may alternatively be provided insegments. Cams 236 may rotate about cam pins 240. Cam pins 240 may bereceived in pin holes 242, for example, in cam clearance slots 238. Withadditional reference to FIGS. 26 and 27, cams 236 may engage drivesurfaces 244 in cam cutouts 246 of endplates 102. Cam cutouts 246 may beformed in lateral sides 124 of endplates 102.

As best on FIG. 28, a cam 236 may comprise a body portion 250, which maybe generally circular in shape, but other shaped body portions 250, suchas square, elliptical, etc., may also be suitable. Cam arms 248 mayextend from body portion 250. Cam arms 248 may engage endplates 102. Forexample, cam arms 248 may engage drive surfaces 244 of endplates 102.The cams 236 may operate to change the direction of the linear movementof cam frame 112. For example, movement of the cam frame 112 along thespacer longitudinal axis 110 may be changed to movement of endplates 102in a direction generally transverse to spacer longitudinal axis 110. Asthe cam frame 112 is moved, for example, along the spacer longitudinalaxis 110, the cams 236 may engage drive surfaces 244 of endplates 102.As best seen on FIG. 26, drive surfaces 244 may be sloped in someembodiments. Cam 236 may rotate as cam frame 112 is moved with cam arms248 pushing endplates 102 relatively apart such that a height of spacer100 may be increased. Cams 236 may be arranged so that expansion may beachieved with advancement or withdrawal of cam frame 112 with movementof the cam frame 112 in the opposite direction causing the cams 236 toengage endplates 102 driving them to a collapsed positon.

Referring now to FIGS. 31-34, in an alternative embodiment, in whichlike numbers correspond to like elements in other embodiments herein, aspacer 100 is illustrated. As illustrated, the spacer 100 may compriseendplates 102 and actuation subassembly 104. Actuation subassembly 104may comprise drive nut 113, drive screw 132, and cam frame 112. Spacer100 may further comprise front plate 174. As previously described, camframe 112 may cams 236 that endplates 102 to drive them outward forcingexpansion of spacer 100. Embodiments of spacer 100, and the variouscomponents thereof, shown on FIGS. 31-37 may be similar in function andoperation to spacer 100 shown on FIGS. 23-30 except that plate body 176of front plate 174 may further include bone fastener receiving holes220. Bone fastener receiving holes 220 may extend through front plate174 at an angle with respect to spacer longitudinal axis 110. Bonefastener receiving holes 220 may be sized and configured to receive abone fastener 222, best seen on FIG. 18. Bone fastener 222 may be anysuitable fastener for securing front plate 174 to adjacent tissue, suchas vertebral bodies. Examples of suitable bone fasteners 222 mayinclude, without limitation, bone screws and bone shanks. As best seenon FIG. 18, front plate 174 may further include a blocking screw 224.Blocking screws 224 may be rotated to block bone fasteners 222 andretain bone fasteners 222 in bone fastener receiving holes 220. Whilespacer 100 shown on FIGS. 31-34 may be implanted using a variety ofapproaches, spacer 100 may be particularly suitable for a lateralapproach.

In some embodiments, spacer 100 may be fabricated using anybiocompatible materials known or hereinafter discovered, havingsufficient strength, flexibility, resiliency, and durability for thepatient, and for the term during which the device is to be implanted.Examples include but are not limited to metal, such as, for exampletitanium and chromium alloys; stainless steel, polymers, including forexample, PEEK or high molecular weight polyethylene (HMWPE); andceramics. There are many other biocompatible materials which may beused, including other plastics and metals, as well as fabrication usingliving or preserved tissue, including autograft, allograft, andxenograft material. Portions or all of the spacer 100 may be radiopaqueor radiolucent, or materials having such properties may be added orincorporated into the spacer 100 to improve imaging of the device duringand after implantation. Any surface or component of a spacer 100 may becoated with or impregnated with therapeutic agents, including bonegrowth, healing, antimicrobial, or drug materials, which may be releasedat a therapeutic rate, using methods known to those skilled in the art.

In some embodiments, spacer 100 may be formed using titanium, or acobalt-chrome-molybdenum alloy, Co—Cr—Mo, for example as specified inASTM F1537 (and ISO 5832-12). The smooth surfaces may be plasma sprayedwith commercially pure titanium, as specified in ASTM F1580, F1978,F1147 and C-633 (and ISO 5832-2). Alternatively, part or all of spacers100 may be formed with a polymer, for example ultra-high molecularweight polyethylene, UHMWPE, for example as specified in ASTM F648 (andISO 5834-2). In one embodiment, PEEK-OPTIMA (a trademark of Invibio LtdCorp, United Kingdom) may be used for one or more components of thedisclosed spacers 100. For example, polymeric portions can be formedwith PEEK-OPTIMA, which is radiolucent, whereby bony ingrowth may beobserved. Other polymeric materials with suitable flexibility,durability, and biocompatibility may also be used.

In accordance with present embodiments, spacer 100 may be provided invarious sizes to best fit the anatomy of the patient. Components ofmatching or divergent sizes may be assembled during the implantationprocedure by a medical practitioner as best meets the therapeutic needsof the patient, the assembly inserted within the body using an insertiontool. In some embodiments, spacer 100 may also be provided with anoverall angular geometry, for example an angular mating disposition ofendplates, to provide for a natural lordosis, or a corrective lordosis,for example of from 0° to 12° for a cervical application, although muchdifferent values may be advantageous for other joints. Lordotic anglesmay also be formed by shaping one or both endplates to have relativelynon-coplanar surfaces.

In some embodiments, a single spacer 100 may be used, to providestabilization for a weakened joint or joint portion. Alternatively, acombination of two, three, or more of any of spacer 100 may be used, ata single joint level, or in multiple joints. Moreover, implants of thedisclosure may be combined with other stabilizing means.

In some embodiments, a spacer 100 may be fabricated using material thatbiodegrades in the body during a therapeutically advantageous timeinterval, for example after sufficient bone ingrowth has taken place.Further, implants of the disclosure are advantageously provided withsmooth and or rounded exterior surfaces, which reduce a potential fordeleterious mechanical effects on neighboring tissues.

In some embodiments, a spacer 100 may be provided to be support adjacentvertebrae during flexion/extension, lateral bending, and axial rotation.In one embodiment, spacer 100 is indicated for spinal arthroplasty intreating skeletally mature patients with degenerative disc disease,primary or recurrent disc herniation, spinal stenosis, or spondylosis inthe lumbosacral spine (LI-SI). The surgery to implant spacer 100 may beperformed through an Anterior, Anterolateral, Posterolateral, Lateral,or any other approach.

The terms “a” or “an”, as used herein, are defined as one or more thanone. The term plurality, as used herein, is defined as two or more thantwo. The term another, as used herein, is defined as at least a secondor more. The terms “including” and “having,” as used herein, are definedas comprising (i.e., open language).

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions andalterations may be made herein without departing from the spirit andscope of the invention as defined by the appended claims

What is claimed is:
 1. A method of separating bones of a joint,comprising: inserting a spacer between bones of the joint; andtranslating a cam frame along a longitudinal axis of the spacer, whereincams disposed on the cam frame engage at least one of a first endplateand a second endplate increasing a height of the spacer.
 2. The methodof claim 1, wherein the spacer is inserted between adjacent vertebralbodies.
 3. The method of claim 1, wherein translating the cam framecauses the cam frame to engage cam pins driving them outward and awayfrom a longitudinal axis of the spacer and, in turn, causes the cam pinsto push the first endplate and the second endplate away from oneanother.
 4. The method of claim 3, wherein the cam pins ride along camslots formed in lateral sides of the cam frame.
 5. The method of claim1, wherein translation the cam frame causes the cams to rotate as thecams engage at least one of the first endplate and the second endplateand push the first endplate and the second endplate away from oneanother.
 6. The method of claim 1, further comprising rotating a drivenut to cause translation of a drive screw and the cam frame, wherein thecam frame is secured to the drive screw such that the cam frame moveswith the drive screw.
 7. The method of claim 6, wherein the drive screwhas a threaded portion that is threadingly coupled to a through bore ofthe drive nut.
 8. The method of claim 6, further comprising pivoting aspacer body with respect to the drive screw to cause articulation of thespacer.
 9. The method of claim 8, wherein the first and second endplatesare disposed on opposite sides of the spacer body.
 10. A method ofseparating bones of a joint, comprising: inserting a spacer betweenbones of the joint, wherein the spacer comprises: a first endplateconfigured to engage a first bone of the joint; a second endplateconfigured to engage a second bone of the joint; and an actuationsubassembly comprising a drive nut, a drive screw coupled to the drivenut, and a cam frame coupled to the drive screw, wherein the cam frameis disposed between the first endplate and the second endplate, whereinthe cam frame comprises a proximal end, a distal end, lateral sides, camslots formed in the lateral sides of the cam frame, and cam pins thatengage the cam slots; and rotating the drive nut to translate the camframe along a longitudinal axis of the spacer, the cam frame engagingthe cam pins to selectively engage at least one of the first endplateand the second endplate to increase a height of the spacer.
 11. Themethod of claim 10, wherein the spacer is moveable from a collapsedposition to an expanded position, wherein, in the expanded position, thespacer has a height that is greater than a height in the collapsedposition.
 12. The method of claim 10, wherein when the cam frame ismoved relative to the first endplate and the second endplate, the campins drive the first endplate and the second endplate away from the camframe to open the spacer.
 13. The method of claim 10, wherein the campins each comprise an elongated body portion and a ridge, wherein theridge is at an angle with respect to the elongated body portion.
 14. Themethod of claim 13, wherein the ridge of each of the cam pins engages acorresponding one of the cam slots.
 15. The method of claim 10, whereinthe drive screw comprises a threaded portion that threadingly engages athrough bore of the drive nut.
 16. The method of claim 10, wherein oneend of the drive screw is retained in an opening in the proximal end,and another end of the drive screw is threadingly coupled to a throughbore of the drive nut.
 17. The method of claim 10, wherein the cam frameis open at the distal end.
 18. The method of claim 10, wherein at leastone retention slot is formed in the proximal end, wherein the at leastone retention slot intersects an opening in the proximal end, andwherein one or more screw retention plates are positioned in the atleast one retention slot to retain the drive screw in the opening. 19.The method of claim 10, wherein the spacer further comprises a frontplate, wherein the front plate comprises a plate body and an extension,wherein the plate body comprises bone fastener receiving holesconfigured to receive bone fasteners, and wherein the extension extendsbetween the first endplate and the second endplate, the drive screwextending through the front plate.
 20. The method of claim 19, whereinthe first endplate further comprises front sockets configured to receivebone fasteners.